1. Field of the Invention
The present invention relates to a traffic engineering method and a node apparatus using the traffic engineering method. More particularly, the present invention relates to a traffic engineering method and a node apparatus using the traffic engineering method in a network.
2. Description of the Related Art
Recently, a great variety of information is being exchanged on the Internet, in areas of not only data communication, but also real-time services providing sounds and images. As a result, the Internet traffic has been increasing rapidly year after year. Thus, a solution is indispensable for a congestion problem on the Internet.
In a network composed of a plurality of nodes, a routing protocol that automatically determines the most appropriate route for forwarding a packet from a source node to a destination node is, for example, an RIP (Routing Information Protocol), an OSPF (Open Shortest Path First), a BGP4 (Border Gateway Protocol Version 4), or an IS-IS (Intermediate System To Intermediate System). In the present network, the most appropriate route for forwarding a packet is determined by use of the above-described protocols, and, then, packet forwarding is carried out on the most appropriate route.
FIG. 1 is a diagram showing a related-art IP packet forwarding process. Generally, each node 10, 11 and 12 shown in FIG. 1 forwards a packet to a destination node by referring to a destination address included in the packet.
A cut-through method has attention as a technology to forward a packet faster than the IP packet forwarding process shown in FIG. 1. For instance, an MPLS (Multi Protocol Label Switching) method is typical of the cut-through method.
FIG. 2 is a diagram showing a related-art IP packet forwarding process by use of the MPLS method. According to the MPLS method, an LSP (Label Switched Path) is initially set on the most appropriate route calculated by a routing protocol, as shown in FIG. 2. Nodes located on both ends of the LSP are called edge nodes 15 and 17. Each node, for example, a node 16 located on the LSP between the edge nodes 15 and 17, or in an MPLS domain, is called a core node.
Next, a label is distributed to each node on the LSP for determining a forwarding direction, by use of an LDP (Label Distribution Protocol). An edge node on a transmitting end, that is, the edge node 15 receives a packet forwarded from the outside of the MPLS domain, and adds a label L1 to the packet. Subsequently, the edge node 15 forwards the packet through the LSP to the core node 16. The core node 16 forwards the packet received from the edge node 15 to an edge node on a receiving end, that is, the edge node 17, by referring to the label L1 and switching the label L1 to a label L2.
At last, the edge node 17 receives the packet from the core node 16, and deletes the label L2 from the packet. The edge node 17, then, forwards the packet to the outside of the MPLS domain. According to the MPLS method, a core node located between edge nodes only needs to forward a packet through a layer 2 by referring to a label, and, thus, a fast packet forwarding process is achieved.
As described above, the fast packet forwarding is achieved by use of the routing protocol and the MPLS technology. However, if traffic increases explosively because of an increase in the number of subscribers on the present Internet, network congestion or packet loss occurs. In conclusion, the MPLS technology has a merit to enable the fast packet forwarding, but has a demerit that the network congestion or the packet loss occurs since the MPLS technology cannot control a packet forwarding path depending on the circumstances by using software such as IP routing in a case in which the traffic is intensive.
Such network congestion and packet loss can be prevented by a traffic engineering (TE), which is a control automatically optimizing entire resources of the network. A traffic engineering function itself does not depend on a layer-2 medium, but is most effectively used on the network as described in the MPLS technology, setting the LSP between a node on a transmitting end and a node on a receiving end.
A load distribution system of the traffic engineering is disclosed in Japanese Priority Application No. 12-12195, for example. The system disclosed in Japanese Priority Application No. 12-12195 sets multi paths LSP1, LSP2 and LSP3 from a transmission node 20 to a reception node 21, as shown in FIG. 3, and distributes traffic of a network among the multi paths LSP1, LSP2 and LSP3, thereby averaging traffic of the entire network.
In detail, in the load distribution system, each node calculates an average usage rate of each link connected to the node, and periodically carries out a flooding process to all the nodes in the load distribution system, in order to recognize a current load on the traffic. The transmission node 20 calculates an effective load on each LSP based on the average usage rate of each link of all the nodes received by the flooding. As illustrated in FIG. 4, the transmission node 20, then, moves the traffic by each micro flow so that the effective loads on all the LSPs become the same value, thereby averaging the loads on the LSPs. The micro flow is a flow used between end users. On the other hand, as illustrated in FIG. 3, an aggregate flow is an aggregation of micro flows having a common destination.
A selection of an LSP, to which a micro flow is mapped, is carried out by use of an LSP decision table shown in FIG. 5A. Every time a new multi path is added to the load distribution system, the number of areas separated in the LSP decision table increases. The transmission node 20 initially calculates a normalized value by using address information included in a packet as a key. The transmission node 20, then, indexes the LSP decision table by use of the normalized value, and decides an LSP, to which the micro flow of the packet is mapped. The transmission node 20 switches the LSP, to which the micro flow is mapped, by moving a boundary of the LSP in the LSP decision table as shown in FIG. 5B, in order to average the traffic of the network. Thus, the load distribution system can distribute the traffic of the network by use of the LSP decision table.
According to the related-art traffic engineering technology described above, a transmission node collects an average usage rate of each link transmitted periodically from all the nodes, and carries out traffic distribution for all the LSPs together after calculating an effective load on each LSP based on the average usage rate of each link. Therefore, the related-art traffic engineering technology enables load balancing in a small-size network. However, the load balancing according to the related-art traffic engineering technology cannot be utilized in a large-size network such as the OSPF routing protocol that includes a plurality of areas, since a load on the transmission node is considerably heavy.
Additionally, according to the related-art traffic engineering technology, in a case in which a route is failed among a plurality of routes, the transmission node can only detect the failed route by using a refresh function of the LDP or detecting a change in a network topology. While searching for the failed route, the load distribution is carried out among the plurality of routes including the failed route. Thus, fast relief of the traffic cannot be achieved by the related-art traffic engineering technology. Additionally, a micro flow such as a TCP (Transmission Control Protocol) connection cannot be relieved.